Office 365 Deployment: Phase 1

I recently presented a session on the Phases of Messaging Deployment for Office 365 at an Ignite training event at Microsoft’s offices in Dallas. I want to share the information I presented in a series of blog posts covering what I see as the four distinct phases of a migration project from on-premises Exchange to Office 365 and Exchange Online.

These four phases are:


This post will cover the topics surrounding Phase 1: Initial Assessment of your on-premises environment.

During this phase you must perform discovery around 4 specific areas:


Using Office 365 can significantly increase your organization’s internet traffic. To prepare for this, you must be sure you have the bandwidth to support all of the following activities:

  • Client Network Traffic
  • Mailbox Migration
  • Desktop Setup
  • NAT & Port Exhaustion

Client Network Traffic

Microsoft provides a useful Java-based tool hosted in Windows Azure (note the URLs below) called the Fast Track Network Analysis tool. This tool performs a number of tests on your internet connection between you and your Office 365 tenant (you must provide the tenant name to begin the tests) including port availability, route summary and performance, speed, consistency of service and VoIP quality readiness among others.

You should run this tool from each distinct office location where users will access your Office 365 tenant.

This tool is available for three distinct regions

North America:




Another useful tool you’ll want to employ is the Exchange Client network Bandwidth Calculator. This Excel spreadsheet allows you to input known data about number and types of clients (Outlook versions, OWA, ActiveSync, etc) and the time zones each of these clients are located. It also uses the familiar User Profile definitions seen in the Exchange Server Role Requirements Calculator that defines usage patterns of your users. The results are a graphical prediction of the amount of bandwidth you’ll need during each hour of the day in order to support all of your users accessing their Office 365 content.



Desktop Setup Bandwidth Impact

If you plan on deploying Office 365 Pro Plus (aka Office 2013) to your users – and even if you’re planning on keeping Office 2007/2010 – there may be bandwidth implications to consider here as well.

Office 2010 (and to a diminishing extent, Office 2007) fully support connectivity with Office 365 resources but require some additional patches and software to do so. You can find a list of required patches in the Office 365 Community web site here and here. In addition to the patches, you must also install the Microsoft Online Services Sign-In Assistant. This tool provides an improved sign-in experience for end users accessing Office 365 services, especially if ADFS is used for Single Sign-In.

If your users have local admin rights on their computers, they can install these patches themselves by logging into the Office 365 portal ( and navigating to the software section to run Desktop Setup. This tool will analyze the computer to determine which patches need to be installed and perform that installation automatically.

Office 365 Pro Plus (Office 2013) supports connectivity to Office 365 “out of the box”. So once you have installed this version of Office, you’re ready to connect to Office 365.

However, if you plan on deploying Office 365 Pro Plus Click-To-Run, there may still be network bandwidth impact. Again, if your users have local admin rights on their computers, you can allow them to use the self-service portal to install Office Pro Plus. Because this installation method is based on the App-V model, it will stream down the bits of the software and allow users to begin using the application within minutes. Too many users installing all at once can have a significant impact on your internet bandwidth availability.

To mitigate this, or in cases where your users have no local admin rights to their computers, you can use the Office Deployment Tool. This tool allows you to stage the installation bits onto an on-premises file server for instance and use a software deployment tool such as System Center or other third-party deployment tool to install the software on users’ computers.


Mailbox Migration Velocity

Many factors can influence how fast you can migrate a mailbox to Office 365. Among them are:

  • MRSProxy Throttling – Your throughput for a single mailbox move will be in the 0.3-1.0 GB/hour range. Maximum average throughput per hour is 10-15GB (100 concurrency). Microsoft will not remote these throttling policies since they’re intended to protect service availability from being impacted by large amounts of users moving to the service. More info:
  • Available On-Premises Bandwidth: – If your mailbox migrations must compete with other user internet traffic for bandwidth, your own connection may become a bottleneck. In these instances, you can setup multiple endpoints to multiple source datacenters (if you have them) to spread the migration load.
  • Packet Loss – Severe packet loss between your on-premises Exchange server and the Office 365 endpoints can cause migrations to experience Transient Exception Errors, causing move requests to pause and/or completely restart.


NAT & Port Exhaustion

Finally, consider how many users you have behind a single public IP address NAT. Outlook clients can use 8 or more connections to Office 365 – more if you consider 3rd-party add-ins (like the social connector that links to LinkedIn and Facebook). With 64,000 available ports behind a single NAT – that means a maximum of 8,000 Outlook users can utilize that NAT – and that’s assuming there aren’t any firewall or proxy servers reserving ports for other uses.


My next post will take up the topic of assessing your on-premises Active Directory and Exchange environments.


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